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Apr 18, 2017
04/17

Apr 18, 2017
by
Lisa Hartung; Anton Klimovsky

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We complete the analysis of the phase diagram of the complex branching Brownian motion energy model by studying Phases I, III and boundaries between all three phases (I-III) of this model. For the properly rescaled partition function, in Phase III and on the boundaries I/III and II/III, we prove a central limit theorem with a random variance. In Phase I and on the boundary I/II, we prove an a.s. and $L^1$ martingale convergence. All results are shown for any given correlation between the real...

Topics: Probability, Disordered Systems and Neural Networks, Condensed Matter, Mathematics

Source: http://arxiv.org/abs/1704.05402

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Mar 19, 2017
03/17

Mar 19, 2017
by
Aser Cortines; Lisa Hartung; Oren Louidor

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We study the structure of extreme level sets of a standard one dimensional branching Brownian motion, namely the sets of particles whose height is within a fixed distance from the order of the global maximum. It is well known that such particles congregate at large times in clusters of order-one genealogical diameter around local maxima which form a Cox process in the limit. We add to these results by finding the asymptotic size of extreme level sets and the typical height and shape of those...

Topics: Probability, Mathematics

Source: http://arxiv.org/abs/1703.06529

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Mar 9, 2017
03/17

Mar 9, 2017
by
Tobias Hartung

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A fully regulated definition of Feynman's path integral is presented here. The proposed re-formulation of the path integral coincides with the familiar formulation whenever the path integral is well-defined. In particular, it is consistent with respect to lattice formulations and Wick rotations, i.e., it can be used in Euclidean and Minkowskian space-time. The path integral regularization is introduced through the generalized Kontsevich-Vishik trace, that is, the extension of the classical...

Topics: Spectral Theory, Mathematical Physics, Quantum Physics, Mathematics

Source: http://arxiv.org/abs/1703.03451

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Feb 28, 2017
02/17

Feb 28, 2017
by
Jeffrey Chilcote; Laurent Pueyo; Robert J. De Rosa; Jeffrey Vargas; Bruce Macintosh; Vanessa P. Bailey; Travis Barman; Brian Bauman; Sebastian Bruzzone; Joanna Bulger; Adam S. Burrows; Andrew Cardwell; Christine H. Chen; Tara Cotten; Daren Dillon; Rene Doyon; Zachary H. Draper; Gaspard Duchêne; Jennifer Dunn; Darren Erikson; Michael P. Fitzgerald; Katherine B. Follette; Donald Gavel; Stephen J. Goodsell; James R. Graham; Alexandra Z. Greenbaum; Markus Hartung; Pascale Hibon; Li-Wei Hung; Patrick Ingraham; Paul Kalas; Quinn Konopacky; James E. Larkin; Jérôme Maire; Franck Marchis; Mark S. Marley; Christian Marois; Stanimir Metchev; Maxwell A. Millar-Blanchaer; Katie M. Morzinski; Eric L. Nielsen; Andrew Norton; Rebecca Oppenheimer; David Palmer; Jennifer Patience; Marshall Perrin; Lisa Poyneer; Abhijith Rajan; Julien Rameau; Fredrik T. Rantakyrö; Naru Sadakuni; Leslie Saddlemyer; Dmitry Savransky; Adam C. Schneider; Andrew Serio; Anand Sivaramakrishnan; Inseok Song; Remi Soummer; Sandrine Thomas; J. Kent Wallace; Jason J. Wang; Kimberly Ward-Duong; Sloane Wiktorowicz; Schuyler Wolff

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Using the Gemini Planet Imager (GPI) located at Gemini South, we measured the near-infrared (1.0-2.4 micron) spectrum of the planetary companion to the nearby, young star $\beta$ Pictoris. We compare the spectrum obtained with currently published model grids and with known substellar objects and present the best matching models as well as the best matching observed objects. Comparing the empirical measurement of the bolometric luminosity to evolutionary models, we find a mass of $12.9\pm0.2$...

Topics: Astrophysics, Earth and Planetary Astrophysics

Source: http://arxiv.org/abs/1703.00011

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Nov 27, 2016
11/16

Nov 27, 2016
by
René van Bevern; Robert Bredereck; Morgan Chopin; Sepp Hartung; Falk Hüffner; André Nichterlein; Ondřej Suchý

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Finding the origin of short phrases propagating through the web has been formalized by Leskovec et al. [ACM SIGKDD 2009] as DAG Partitioning: given an arc-weighted directed acyclic graph on $n$ vertices and $m$ arcs, delete arcs with total weight at most $k$ such that each resulting weakly-connected component contains exactly one sink---a vertex without outgoing arcs. DAG Partitioning is NP-hard. We show an algorithm to solve DAG Partitioning in $O(2^k \cdot (n+m))$ time, that is, in linear...

Topics: Discrete Mathematics, Data Structures and Algorithms, Computing Research Repository, Social and...

Source: http://arxiv.org/abs/1611.08809

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Nov 25, 2016
11/16

Nov 25, 2016
by
Andreas Ammon; Alan Genz; Tobias Hartung; Karl Jansen; Hernan Leövey; Julia Volmer

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The error scaling for Markov-Chain Monte Carlo techniques (MCMC) with $N$ samples behaves like $1/\sqrt{N}$. This scaling makes it often very time intensive to reduce the error of computed observables, in particular for applications in lattice QCD. It is therefore highly desirable to have alternative methods at hand which show an improved error scaling. One candidate for such an alternative integration technique is the method of recursive numerical integration (RNI). The basic idea of this...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1611.08628

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Oct 6, 2016
10/16

Oct 6, 2016
by
Andreas Ammon; Tobias Hartung; Karl Jansen; Hernan Leövey; Julia Volmer

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In lattice Quantum Field Theory, we are often presented with integrals over polynomials of coefficients of matrices in U(N) or SU(N) with respect to the Haar measure. In some physical situations, e.g., in presence of a chemical potential, these integrals are numerically very difficult since their integrands are highly oscillatory which manifests itself in form of the sign problem. In these cases, Monte Carlo methods often fail to be adequate, rendering such computations practically impossible....

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1610.01931

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Jul 27, 2016
07/16

Jul 27, 2016
by
Sebastian Andres; Lisa Hartung

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We construct a class of one-dimensional diffusion processes on the particles of branching Brownian motion that are symmetric with respect to the limits of random martingale measures. These measures are associated with the extended extremal process of branching Brownian motion and are supported on a Cantor-like set. The processes are obtained via a time-change of a standard one-dimensional reflected Brownian motion on $\mathbb{R}_+$ in terms of the associated positive continuous additive...

Topics: Probability, Mathematics

Source: http://arxiv.org/abs/1607.08132

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Jul 18, 2016
07/16

Jul 18, 2016
by
A. Ammon; T. Hartung; K. Jansen; H. Leövey; J. Volmer

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In this paper we describe a new integration method for the groups $U(N)$ and $SU(N)$, for which we verified numerically that it is polynomially exact for $N\le 3$. The method is applied to the example of 1-dimensional QCD with a chemical potential. We explore, in particular, regions of the parameter space in which the sign problem appears due the presence of the chemical potential. While Markov Chain Monte Carlo fails in this region, our new integration method still provides results for the...

Topics: Numerical Analysis, High Energy Physics - Lattice, Mathematics

Source: http://arxiv.org/abs/1607.05027

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Jun 23, 2016
06/16

Jun 23, 2016
by
S. Eckart; M. Richter; M. Kunitski; A. Hartung; J. Rist; K. Henrichs; N. Schlott; H. Kang; T. Bauer; H. Sann; L. Ph. H. Schmidt; M. Schöffler; T. Jahnke; R. Dörner

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We report on non-sequential double ionization of Ar by a laser pulse consisting of two counter rotating circularly polarized fields (390 nm and 780 nm). The double ionization probability depends strongly on the relative intensity of the two fields and shows a "knee"-like structure as function of intensity. We conclude that double ionization is driven by a beam of nearly monoenergetic recolliding electrons, which can be controlled in intensity and energy by the field parameters. The...

Topics: Atomic Physics, Physics

Source: http://arxiv.org/abs/1606.07303

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0.0

Apr 5, 2016
04/16

Apr 5, 2016
by
Robert J. De Rosa; Julien Rameau; Jenny Patience; James R. Graham; René Doyon; David Lafrenière; Bruce Macintosh; Laurent Pueyo; Abhijith Rajan; Jason J. Wang; Kimberly Ward-Duong; Li-Wei Hung; Jérôme Maire; Eric L. Nielsen; S. Mark Ammons; Joanna Bulger; Andrew Cardwell; Jeffrey K. Chilcote; Ramon L. Galvez; Benjamin L. Gerard; Stephen Goodsell; Markus Hartung; Pascale Hibon; Patrick Ingraham; Mara Johnson-Groh; Paul Kalas; Quinn M. Konopacky; Franck Marchis; Christian Marois; Stanimir Metchev; Katie M. Morzinski; Rebecca Oppenheimer; Marshall D. Perrin; Fredrik T. Rantakyrö; Dmitry Savransky; Sandrine Thomas

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We present new $H$ (1.5-1.8 $\mu$m) photometric and $K_1$ (1.9-2.2 $\mu$m) spectroscopic observations of the young exoplanet HD 95086 b obtained with the Gemini Planet Imager. The $H$-band magnitude has been significantly improved relative to previous measurements, whereas the low resolution $K_1$ ($\lambda/\delta\lambda \approx 66$) spectrum is featureless within the measurement uncertainties, and presents a monotonically increasing pseudo-continuum consistent with a cloudy atmosphere. By...

Topics: Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1604.01411

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Mar 15, 2016
03/16

Mar 15, 2016
by
J. R. Calvey; W. Hartung; J. Makita; M. Venturini

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The buildup of low energy electrons in an accelerator, known as electron cloud, can be severely detrimental to machine performance. Under certain beam conditions, the beam can become resonant with the cloud dynamics, accelerating the buildup of electrons. This paper will examine two such effects: multipacting resonances, in which the cloud development time is resonant with the bunch spacing, and cyclotron resonances, in which the cyclotron period of electrons in a magnetic field is a multiple...

Topics: Accelerator Physics, Physics

Source: http://arxiv.org/abs/1603.04817

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Jan 26, 2016
01/16

Jan 26, 2016
by
Schuyler G. Wolff; Marshall Perrin; Maxwell A. Millar-Blanchaer; Eric L. Nielsen; Jason Wang; Andrew Cardwell; Jeffrey Chilcote; Ruobing Dong; Zachary H. Draper; Gaspard Duchene; Michael P. Fitzgerald; Stephen J. Goodsell; Carol A. Grady; James R. Graham; Alexandra Z. Greenbaum; Markus Hartung; Pascale Hibon; Dean C. Hines; Li-Wei Hung; Paul Kalas; Bruce Macintosh; Franck Marchis; Christian Marois; Laurent Pueyo; Fredrik T. Rantakyro; Glenn Schneider; Anand Sivaramakrishnan; Sloane J. Wiktorowicz

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We present H and K band imaging polarimetry for the PDS 66 circumstellar disk obtained during the commissioning of the Gemini Planet Imager (GPI). Polarization images reveal a clear detection of the disk in to the 0.12'' inner working angle (IWA) in H band, almost 3 times as close to the star as the previous HST observations with NICMOS and STIS (0.35'' effective IWA). The centro-symmetric polarization vectors confirm that the bright inner disk detection is due to circumstellar scattered light....

Topics: Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1601.07248

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Jan 13, 2016
01/16

Jan 13, 2016
by
S. Zeller; M. Kunitski; J. Voigtsberger; A. Kalinin; A. Schottelius; C. Schober; M. Waitz; H. Sann; A. Hartung; T. Bauer; M. Pitzer; F. Trinter; C. Goihl; C. Janke; M. Richter; G. Kastirke; M. Weller; A. Czasch; M. Kitzler; M. Braune; R. E. Grisenti; W. Schöllkopf; L. Ph. H. Schmidt; M. Schöffer; J. B. Williams; T. Jahnke; R. Dörner

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We report on coulomb explosion imaging of the wavefunction of the quantum halo system He$_2$. Each atom of this system is ionized by tunnelionization in a femto second laser pulse and in a second experiment by single photon ionization employing a free electron laser. We visualize the exponential decay of the probability density of the tunneling particle over distance for over two orders of magnitude up to an internuclear distance of 250 {\AA}. By fitting the slope of the density in the...

Topics: Atomic Physics, Nuclear Experiment, Atomic and Molecular Clusters, Chemical Physics, Physics

Source: http://arxiv.org/abs/1601.03247

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1.0

Dec 17, 2015
12/15

Dec 17, 2015
by
Laurent Bulteau; Vincent Froese; Sepp Hartung; Rolf Niedermeier

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Co-clustering, that is, partitioning a numerical matrix into homogeneous submatrices, has many applications ranging from bioinformatics to election analysis. Many interesting variants of co-clustering are NP-hard. We focus on the basic variant of co-clustering where the homogeneity of a submatrix is defined in terms of minimizing the maximum distance between two entries. In this context, we spot several NP-hard as well as a number of relevant polynomial-time solvable special cases, thus...

Topics: Discrete Mathematics, Computing Research Repository

Source: http://arxiv.org/abs/1512.05693

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1.0

Oct 25, 2015
10/15

Oct 25, 2015
by
Tobias Hartung; Simon Scott

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Based on Guillemin's work on gauged Lagrangian distributions, we will introduce the notion of a poly-$\log$-homogeneous distribution as an approach to $\zeta$-functions for a class of Fourier Integral Operators which includes cases of amplitudes with asymptotic expansion $\sum_{k\in\mathbb{N}}a_{m_k}$ where each $a_{m_k}$ is $\log$-homogeneous with degree of homogeneity $m_k$ but violating $\Re(m_k)\to-\infty$. We will calculate the Laurent expansion for the $\zeta$-function and give formulae...

Topics: Analysis of PDEs, Operator Algebras, Spectral Theory, Mathematics, Classical Analysis and ODEs

Source: http://arxiv.org/abs/1510.07324

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Aug 19, 2015
08/15

Aug 19, 2015
by
Maxwell A. Millar-Blanchaer; James R. Graham; Laurent Pueyo; Paul Kalas; Rebekah I. Dawson; Jason Wang; Marshall Perrin; Dae-Sik Moon; Bruce Macintosh; S. Mark Ammons; Travis Barman; Andrew Cardwell; Christine H. Chen; Eugene Chiang; Jeffrey Chilcote; Tara Cotten; Robert J. De Rosa; Zachary H. Draper; Jennifer Dunn; Gaspard Duchêne; Thomas M. Esposito; Michael P. Fitzgerald; Katherine B. Follette; Stephen J. Goodsell; Alexandra Z. Greenbaum; Markus Hartung; Pascale Hibon; Sasha Hinkley; Patrick Ingraham; Rebecca Jensen-Clem; Quinn Konopacky; James E. Larkin; Douglas Long; Jérôme Maire; Franck Marchis; Mark S. Marley; Christian Marois; Katie M. Morzinski; Eric L. Nielsen; David W. Palmer; Rebecca Oppenheimer; Lisa Poyneer; Abhijith Rajan; Fredrik T. Rantakyrö; Jean-Baptiste Ruffio; Naru Sadakuni; Leslie Saddlemyer; Adam C. Schneider; Anand Sivaramakrishnan; Remi Soummer; Sandrine Thomas; Gautam Vasisht; David Vega; J. Kent Wallace; Kimberly Ward-Duong; Sloane J. Wiktorowicz; Schuyler G. Wolff

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We present $H$-band observations of $\beta$ Pic with the Gemini Planet Imager's (GPI's) polarimetry mode that reveal the debris disk between ~0.3" (~6 AU) and ~1.7" (~33 AU), while simultaneously detecting $\beta$ Pic $b$. The polarized disk image was fit with a dust density model combined with a Henyey-Greenstein scattering phase function. The best fit model indicates a disk inclined to the line of sight ($\phi=85.27{\deg}^{+0.26}_{-0.19}$) with a position angle...

Topics: Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1508.04787

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Aug 19, 2015
08/15

Aug 19, 2015
by
Jason J. Wang; James R. Graham; Laurent Pueyo; Eric L. Nielsen; Max Millar-Blanchaer; Robert J. De Rosa; Paul Kalas; S. Mark Ammons; Joanna Bulger; Andrew Cardwell; Christine Chen; Eugene Chiang; Jeffrey K. Chilcote; René Doyon; Zachary H. Draper; Gaspard Duchêne; Thomas M. Esposito; Michael P. Fitzgerald; Stephen J. Goodsell; Alexandra Z. Greenbaum; Markus Hartung; Pascale Hibon; Sasha Hinkley; Li-Wei Hung; Patrick Ingraham; James E. Larkin; Bruce Macintosh; Jerome Maire; Franck Marchis; Christian Marois; Brenda C. Matthews; Katie M. Morzinski; Rebecca Oppenheimer; Jenny Patience; Marshall D. Perrin; Abhijith Rajan; Fredrik T. Rantakyrö; Naru Sadakuni; Andrew Serio; Anand Sivaramakrishnan; Rémi Soummer; Sandrine Thomas; Kimberly Ward-Duong; Sloane J. Wiktorowicz; Schuyler G. Wolff

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We present Gemini Planet Imager (GPI) observations of AU Microscopii, a young M dwarf with an edge-on, dusty debris disk. Integral field spectroscopy and broadband imaging polarimetry were obtained during the commissioning of GPI. In our broadband imaging polarimetry observations, we detect the disk only in total intensity and find asymmetries in the morphology of the disk between the southeast and northwest sides. The southeast side of the disk exhibits a bump at 1$''$ (10 AU projected...

Topics: Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1508.04765

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1.0

Apr 20, 2015
04/15

Apr 20, 2015
by
Lisa Hartung; Anton Klimovsky

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We identify the fluctuations of the partition function for a class of random energy models, where the energies are given by the positions of the particles of the complex-valued branching Brownian motion (BBM). Specifically, we provide the weak limit theorems for the partition function in the so-called "glassy phase" -- the regime of parameters, where the behaviour of the partition function is governed by the extrema of BBM. We allow for arbitrary correlations between the real and...

Topics: Condensed Matter, Probability, Disordered Systems and Neural Networks, Mathematics

Source: http://arxiv.org/abs/1504.05097

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2.0

Mar 17, 2015
03/15

Mar 17, 2015
by
A. Ammon; A. Genz; T. Hartung; K. Jansen; H. Leövey; J. Volmer

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We apply the Quasi Monte Carlo (QMC) and recursive numerical integration methods to evaluate the Euclidean, discretized time path-integral for the quantum mechanical anharmonic oscillator and a topological quantum mechanical rotor model. For the anharmonic oscillator both methods outperform standard Markov Chain Monte Carlo methods and show a significantly improved error scaling. For the quantum mechanical rotor we could, however, not find a successful way employing QMC. On the other hand, the...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1503.05088

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0.0

Dec 18, 2014
12/14

Dec 18, 2014
by
Anton Bovier; Lisa Hartung

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We extend the results of Arguin et al and A\"\i{}d\'ekon et al on the convergence of the extremal process of branching Brownian motion by adding an extra dimension that encodes the "location" of the particle in the underlying Galton-Watson tree. We show that the limit is a cluster point process on $\mathbb{R}_+\times \mathbb{R}$ where each cluster is the atom of a Poisson point process on $\mathbb{R}_+\times \mathbb{R}$ with a random intensity measure $Z(dz) \times Ce^{-\sqrt...

Topics: Probability, Mathematics

Source: http://arxiv.org/abs/1412.5975

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Dec 18, 2014
12/14

Dec 18, 2014
by
Thomas Isele; Benedikt Hartung; Philipp Hövel; Eckehard Schöll

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We examine traveling-wave solutions on a regular ring network with one additional long-range link that spans a distance d. The nodes obey the FitzHugh-Nagumo kinetics in the excitable regime. The additional shortcut induces a plethora of spatio-temporal behavior that is not present without it. We describe the underlying mechanisms for different types of patterns: propagation failure, period decreasing, bistability, shortcut blocking and period multiplication. For this purpose, we investigate...

Topics: Nonlinear Sciences, Adaptation and Self-Organizing Systems

Source: http://arxiv.org/abs/1412.5970

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0.0

Dec 10, 2014
12/14

Dec 10, 2014
by
W. H. Hartung; D. M. Asner; J. V. Conway; C. A. Dennett; S. Greenwald; J. -S. Kim; Y. Li; T. P. Moore; V. Omanovic; M. A. Palmer; C. R. Strohman

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The performance of a particle accelerator can be limited by the build-up of an electron cloud (EC) in the vacuum chamber. Secondary electron emission from the chamber walls can contribute to EC growth. An apparatus for in-situ measurements of the secondary electron yield (SEY) in the Cornell Electron Storage Ring (CESR) was developed in connection with EC studies for the CESR Test Accelerator program. The CESR in-situ system, in operation since 2010, allows for SEY measurements as a function of...

Topics: Accelerator Physics, Physics, Instrumentation and Detectors

Source: http://arxiv.org/abs/1412.3477

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3.0

Nov 3, 2014
11/14

Nov 3, 2014
by
Thomas L. Hayward; Beth A. Biller; Michael C. Liu; Eric L. Nielsen; Zahed Wahhaj; Mark Chun; Christ Ftaclas; Markus Hartung; Douglas W. Toomey

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We describe the astrometric calibration of the Gemini NICI Planet-Finding Campaign. The Campaign requires a relative astrometric accuracy of $\approx$ 20 mas across multi-year timescales in order to distinguish true companions from background stars by verifying common proper motion and parallax with their parent stars. The calibration consists of a correction for instrumental optical image distortion, plus on-sky imaging of astrometric fields to determine the pixel scale and image orientation....

Topics: Instrumentation and Methods for Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1411.0641

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0.0

Sep 18, 2014
09/14

Sep 18, 2014
by
Patrick Ingraham; Mark S. Marley; Didier Saumon; Christian Marois; Bruce Macintosh; Travis Barman; Brian Bauman; Adam Burrows; Jeffrey K. Chilcote; Robert J. De Rosa; Daren Dillon; Rene Doyon; Jennifer Dunn; Darren Erikson; Michael P. Fitzgerald; Donald Gavel; Stephen J. Goodsell; James R. Graham; Markus Hartung; Pascale Hibon; Paul G. Kalas; Quinn Konopacky; James A. Larkin; Jerome Maire; Franck Marchis; James McBride; Max Millar-Blanchaer; Katie M. Morzinski; Andrew Norton; Rebecca Oppenheimer; Dave W. Palmer; Jenny Patience; Marshall D. Perrin; Lisa A. Poyneer; Laurent Pueyo; Fredrik Rantakyro; Naru Sadakuni; Leslie Saddlemyer; Dmitry Savransky; Remi Soummer; Anand Sivaramakrishnan; Inseok Song; Sandrine Thomas; J. Kent Wallace; Sloane J. Wiktorowicz; Schuyler G. Wolff

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During the first-light run of the Gemini Planet Imager (GPI) we obtained K-band spectra of exoplanets HR 8799 c and d. Analysis of the spectra indicates that planet d may be warmer than planet c. Comparisons to recent patchy cloud models and previously obtained observations over multiple wavelengths confirm that thick clouds combined with horizontal variation in the cloud cover generally reproduce the planets' spectral energy distributions. When combined with the 3 to 4 um photometric data...

Topics: Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1409.5456

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1.0

Aug 22, 2014
08/14

Aug 22, 2014
by
J. R. Calvey; W. Hartung; Y. Li; J. A. Livezey; J. Makita; M. A. Palmer; D. Rubin

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Retarding field analyzers (RFAs), which provide a localized measurement of the electron cloud, have been installed throughout the Cornell Electron Storage Ring (CESR), in different magnetic field environments. This paper describes the RFA designs developed for dipole, quadrupole, and wiggler field regions, and provides an overview of measurements made in each environment. The effectiveness of electron cloud mitigations, including coatings, grooves, and clearing electrodes, are assessed with the...

Topics: Accelerator Physics, Physics

Source: http://arxiv.org/abs/1408.5741

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Aug 18, 2014
08/14

Aug 18, 2014
by
Muller, Clemens R; Skirde, Judith; Hartung, Edmund; Anetseder, Martin; Ricci, Yvonne; Islander, Gunilla; Schuster, Frank

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This article is from BMC Anesthesiology , volume 14 . Abstract None

Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4139662

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90

Aug 18, 2014
08/14

Aug 18, 2014
by
Hartung, Viktor; Prell, Tino; Gaser, Christian; Turner, Martin R.; Tietz, Florian; Ilse, Benjamin; Bokemeyer, Martin; Witte, Otto W.; Grosskreutz, Julian

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This article is from PLoS ONE , volume 9 . Abstract Amyotrophic lateral sclerosis (ALS) is characterized by progressive loss of upper and lower motor neurons. Advanced MRI techniques such as diffusion tensor imaging have shown great potential in capturing a common white matter pathology. However the sensitivity is variable and diffusion tensor imaging is not yet applicable to the routine clinical environment. Voxel-based morphometry (VBM) has revealed grey matter changes in ALS, but the...

Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4136773

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0.0

Jul 29, 2014
07/14

Jul 29, 2014
by
Markus Hartung; Bruce Macintosh; Paul Langlois; Naru Sadakuni; Don Gavel; J. Kent Wallace; Dave Palmer; Lisa Poyneer; Dmitry Savransky; Sandrine Thomas; Darren Dillon; Jennifer Dunn; Pascal Hibon; Fredrik Rantakyro; Stephen Goodsell

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The Gemini Planet Imager (GPI) entered on-sky commissioning phase, and had its First Light at the Gemini South telescope in November 2013. Meanwhile, the fast loops for atmospheric correction of the Extreme Adaptive Optics (XAO) system have been closed on many dozen stars at different magnitudes (I=4-8), elevation angles and a variety of seeing conditions, and a stable loop performance was achieved from the beginning. Ultimate contrast performance requires a very low residual wavefront error...

Topics: Instrumentation and Methods for Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.7895

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1.0

Jul 29, 2014
07/14

Jul 29, 2014
by
Markus Hartung; Tom Hayward; Les Saddlemyer; Lisa Poyneer; Andrew Cardwell; Chas Cavedoni; Myung Cho; Jeffrey K. Chilcote; Paul Collins; Darren Dillon; Ramon Galvez; Gaston Gausachs; Stephen Goodsell; Andres Guesalaga; Pascal Hibon; James Larkin; Bruce Macintosh; Dave Palmer; Naru Sadakuni; Dmitry Savransky; Andrew Serio; Fredrik Rantakyro; Kent Wallace

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The Gemini Planet Imager (GPI) entered on-sky commissioning and had its first-light at the Gemini South (GS) telescope in November 2013. GPI is an extreme adaptive optics (XAO), high-contrast imager and integral-field spectrograph dedicated to the direct detection of hot exo-planets down to a Jupiter mass. The performance of the apodized pupil Lyot coronagraph depends critically upon the residual wavefront error (design goal of 60 nm RMS with 5 mas RMS tip/tilt), and therefore is most sensitive...

Topics: Instrumentation and Methods for Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.7893

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Jul 28, 2014
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Jul 28, 2014
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Becker, Martina; Guttler, Steffen; Bachem, Annabell; Hartung, Evelyn; Mora, Ahmed; Jakel, Anika; Hutloff, Andreas; Henn, Volker; Mages, Hans Werner; Gurka, Stephanie; Kroczek, Richard A.

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This article is from Frontiers in Immunology , volume 5 . Abstract In the past, lack of lineage markers confounded the classification of dendritic cells (DC) in the intestine and impeded a full understanding of their location and function. We have recently shown that the chemokine receptor XCR1 is a lineage marker for cross-presenting DC in the spleen. Now, we provide evidence that intestinal XCR1+ DC largely, but not fully, overlap with CD103+ CD11b− DC, the hypothesized correlate of...

Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4112810

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Jul 16, 2014
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Jul 16, 2014
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Jeffrey Chilcote; Travis Barman; Michael P. Fitzgerald; James R. Graham; James E. Larkin; Bruce Macintosh; Brian Bauman; Adam S. Burrows; Andrew Cardwell; Robert J. De Rosa; Daren Dillon; Rene Doyon; Jennifer Dunn; Darren Erikson; Donald Gavel; Stephen J. Goodsell; Markus Hartung; Pascale Hibon; Patrick Ingraham; Paul Kalas; Quinn Konopacky; Jérôme Maire; Franck Marchis; Mark S. Marley; Christian Marois; Max Millar-Blanchaer; Katie Morzinski; Andrew Norton; B. R. Oppenheimer; David Palmer; Jennifer Patience; Marshall D. Perrin; Lisa Poyneer; Laurent Pueyo; Fredrik Rantakyrö; Naru Sadakuni; Leslie Saddlemyer; Dmitry Savransky; Andrew Serio; Anand Sivaramakrishnan; Inseok Song; Remi Soummer; Sandrine Thomas; J. Kent Wallace; Sloane J. Wiktorowicz; Schuyler Wolff

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Using the recently installed Gemini Planet Imager (GPI), we have taken the first H-band spectrum of the planetary companion to the nearby young star beta Pictoris. GPI is designed to image and provide low-resolution spectra of Jupiter sized, self-luminous planetary companions around young nearby stars. These observations were taken covering the H-band (1.65 microns). The spectrum has a resolving power of $\sim$ 45 and demonstrates the distinctive triangular shape of a cool substellar object...

Topics: Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.4469

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Jul 10, 2014
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Jul 10, 2014
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Santos-Garcia, Diego; Latorre, Amparo; Moya, Andres; Gibbs, George; Hartung, Viktor; Dettner, Konrad; Kuechler, Stefan Martin; Silva, Francisco J.

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This article is from Genome Biology and Evolution , volume 6 . Abstract Moss bugs (Coleorrhyncha: Peloridiidae) are members of the order Hemiptera, and like many hemipterans, they have symbiotic associations with intracellular bacteria to fulfill nutritional requirements resulting from their unbalanced diet. The primary endosymbiont of the moss bugs, Candidatus Evansia muelleri, is phylogenetically related to Candidatus Carsonella ruddii and Candidatus Portiera aleyrodidarum, primary...

Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4122945

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Jul 9, 2014
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Jul 9, 2014
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Marshall D. Perrin; Gaspard Duchene; Max Millar-Blanchaer; Michael P. Fitzgerald; James R. Graham; Sloane J. Wiktorowicz; Paul G. Kalas; Bruce Macintosh; Brian Bauman; Andrew Cardwell; Jeffrey Chilcote; Robert J. De Rosa; Daren Dillon; René Doyon; Jennifer Dunn; Donald Gavel; Stephen Goodsell; Markus Hartung; Pascale Hibon; Patrick Ingraham; Daniel Kerley; Quinn Konapacky; James E. Larkin; Jérôme Maire; Franck Marchis; Christian Marois; Tushar Mittal; Katie M. Morzinski; B. R. Oppenheimer; David W. Palmer; Jennifer Patience; Lisa Poyneer; Laurent Pueyo; Fredrik T. Rantakyrö; Naru Sadakuni; Leslie Saddlemyer; Dmitry Savransky; Rémi Soummer; Anand Sivaramakrishnan; Inseok Song; Sandrine Thomas; J. Kent Wallace; Jason J. Wang; Schuyler G. Wolff

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We present the first results from the polarimetry mode of the Gemini Planet Imager (GPI), which uses a new integral field polarimetry architecture to provide high contrast linear polarimetry with minimal systematic biases between the orthogonal polarizations. We describe the design, data reduction methods, and performance of polarimetry with GPI. Point spread function subtraction via differential polarimetry suppresses unpolarized starlight by a factor of over 100, and provides sensitivity to...

Topics: Instrumentation and Methods for Astrophysics, Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.2495

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Jul 8, 2014
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Jul 8, 2014
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Marshall D. Perrin; Jérôme Maire; Patrick Ingraham; Dmitry Savransky; Max Millar-Blanchaer; Schuyler G. Wolff; Jean-Baptiste Ruffio; Jason J. Wang; Zachary H. Draper; Naru Sadakuni; Christian Marois; Abhijith Rajan; Michael P. Fitzgerald; Bruce Macintosh; James R. Graham; René Doyon; James E. Larkin; Jeffrey K. Chilcote; Stephen J. Goodsell; David W. Palmer; Kathleen Labrie; Mathilde Beaulieu; Robert J. De Rosa; Alexandra Z. Greenbaum; Markus Hartung; Pascale Hibon; Quinn Konopacky; David Lafreniere; Jean-Francois Lavigne; Franck Marchis; Jenny Patience; Laurent Pueyo; Fredrik T. Rantakyrö; Rémi Soummer; Anand Sivaramakrishnan; Sandrine Thomas; Kimberly Ward-Duong; Sloane Wiktorowicz

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The Gemini Planet Imager (GPI) has as its science instrument an infrared integral field spectrograph/polarimeter (IFS). Integral field spectrographs are scientificially powerful but require sophisticated data reduction systems. For GPI to achieve its scientific goals of exoplanet and disk characterization, IFS data must be reconstructed into high quality astrometrically and photometrically accurate datacubes in both spectral and polarization modes, via flexible software that is usable by the...

Topics: Instrumentation and Methods for Astrophysics, Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.2301

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Jul 8, 2014
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Jul 8, 2014
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Alexandra Z. Greenbaum; Anthony Cheetham; Anand Sivaramakrishnan; Peter Tuthill; Barnaby Norris; Laurent Pueyo; Naru Sadakuni; Fredrik Rantakyrö; Pascale Hibon; Stephen Goodsell; Markus Hartung; Andrew Serio; Andrew Cardwell; Lisa Poyneer; Bruce Macintosh; Dmitry Savransky; Marshall D. Perrin; Schuyler Wolff; Patrick Ingraham; Sandrine Thomas; with the GPI team

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The Gemini Planet Imager (GPI) Extreme Adaptive Optics Coronograph contains an interferometric mode: a 10-hole non-redundant mask (NRM) in its pupil wheel. GPI operates at $Y, J, H$, and $K$ bands, using an integral field unit spectrograph (IFS) to obtain spectral data at every image pixel. NRM on GPI is capable of imaging with a half resolution element inner working angle at moderate contrast, probing the region behind the coronagraphic spot. The fine features of the NRM PSF can provide a...

Topics: Instrumentation and Methods for Astrophysics, Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.2310

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Jul 8, 2014
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Jul 8, 2014
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Fredrik T. Rantakyrö; Andrew Cardwell; Jeffrey Chilcote; Jennifer Dunn; Stephen Goodsell; Pascale Hibon; Bruce Macintosh; Carlos Quiroz; Marshall D. Perrin; Naru Sadakuni; Leslie Saddlemyer; Dmitry Savransky; Andrew Serio; Claudia Winge; Ramon Galvez; Gaston Gausachs; Kayla Hardie; Markus Hartung; Javier Luhrs; Lisa Poyneer; Sandrine Thomas

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The Gemini Planet Imager is an extreme AO instrument with an integral field spectrograph (IFS) operating in Y, J, H, and K bands. Both the Gemini telescope and the GPI instrument are very complex systems. Our goal is that the combined telescope and instrument system may be run by one observer operating the instrument, and one operator controlling the telescope and the acquisition of light to the instrument. This requires a smooth integration between the two systems and easily operated control...

Topics: Instrumentation and Methods for Astrophysics, Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.2311

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Jul 8, 2014
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Jul 8, 2014
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Naru Sadakuni; Bruce A. Macintosh; David W. Palmer; Lisa A. Poyneer; Claire E. Max; Dmitry Savransky; Sandrine J. Thomas; Andrew Cardwell; Stephen Goodsell; Markus Hartung; Pascale Hibon; Fredrik Rantakyrö; Andrew Serio; with the GPI team

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The Gemini Planet Imager (GPI) is a new facility, extreme adaptive optics (AO), coronagraphic instrument, currently being integrated onto the 8-meter Gemini South telescope, with the ultimate goal of directly imaging extrasolar planets. To achieve the contrast required for the desired science, it is necessary to quantify and mitigate wavefront error (WFE). A large source of potential static WFE arises from the primary AO wavefront sensor (WFS) detector's use of multiple readout segments with...

Topics: Instrumentation and Methods for Astrophysics, Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.2316

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Jul 8, 2014
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Jul 8, 2014
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Dmitry Savransky; Sandrine J. Thomas; Lisa A. Poyneer; Jennifer Dunn; Bruce A. Macintosh; Naru Sadakuni; Daren Dillon; Stephen J. Goodsell; Markus Hartung; Pascale Hibon; Fredrik Rantakyrö; Andrew Cardwell; Andrew Serio; with the GPI team

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The Gemini Planet Imager (GPI) is a next-generation, facility instrument currently being commissioned at the Gemini South observatory. GPI combines an extreme adaptive optics system and integral field spectrograph (IFS) with an apodized-pupil Lyot coronagraph (APLC) producing an unprecedented capability for directly imaging and spectroscopically characterizing extrasolar planets. GPI's operating goal of $10^{-7}$ contrast requires very precise alignments between the various elements of the...

Topics: Instrumentation and Methods for Astrophysics, Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.2313

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Jul 8, 2014
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Jul 8, 2014
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Sloane J. Wiktorowicz; Max Millar-Blanchaer; Marshall D. Perrin; James R. Graham; Michael P. Fitzgerald; Jérôme Maire; Patrick Ingraham; Dmitry Savransky; Bruce A. Macintosh; Sandrine J. Thomas; Jeffrey K. Chilcote; Zachary H. Draper; Inseok Song; Andrew Cardwell; Stephen J. Goodsell; Markus Hartung; Pascale Hibon; Fredrik Rantakyrö; Naru Sadakuni; the GPI team

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We present on-sky polarimetric observations with the Gemini Planet Imager (GPI) obtained at straight Cassegrain focus on the Gemini South 8-m telescope. Observations of polarimetric calibrator stars, ranging from nearly unpolarized to strongly polarized, enable determination of the combined telescope and instrumental polarization. We find the conversion of Stokes $I$ to linear and circular instrumental polarization in the instrument frame to be $I \rightarrow (Q_{\rm IP}, U_{\rm IP}, P_{\rm...

Topics: Instrumentation and Methods for Astrophysics, Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.2307

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Jul 8, 2014
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Jul 8, 2014
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Pascale Hibon; Sandrine Thomas; Jennifer Dunn; Jenny Atwood; Les Saddlemyer; Naru Sadakuni; Stephen Goodsell; Bruce Macintosh; James Graham; Marshall Perrin; Fredrik Rantakyrö; Vincent Fesquet; Andrew Serio; Carlos Quiroz; Andrew Cardwell; Gaston Gausachs; Dmitry Savransky; Dan Kerley; Markus Hartung; Ramon Galvez; Kayla Hardie

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An Atmospheric Dispersion Corrector (ADC) uses a double-prism arrangement to nullify the vertical chromatic dispersion introduced by the atmosphere at non-zero zenith distances. The ADC installed in the Gemini Planet Imager (GPI) was first tested in August 2012 while the instrument was in the laboratory. GPI was installed at the Gemini South telescope in August 2013 and first light occurred later that year on November 11th. In this paper, we give an overview of the characterizations and...

Topics: Instrumentation and Methods for Astrophysics, Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.2315

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Jul 8, 2014
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Jul 8, 2014
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Lisa A. Poyneer; Robert J. De Rosa; Bruce Macintosh; David W. Palmer; Marshall D. Perrin; Naru Sadakuni; Dmitry Savransky; Brian Bauman; Andrew Cardwell; Jeffrey K. Chilcote; Daren Dillon; Donald Gavel; Stephen J. Goodsell; Markus Hartung; Pascale Hibon; Fredrik T. Rantakyro; Sandrine Thomas; Jean-Pierre Veran

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The Gemini Planet Imager instrument's adaptive optics (AO) subsystem was designed specifically to facilitate high-contrast imaging. It features several new technologies, including computationally efficient wavefront reconstruction with the Fourier transform, modal gain optimization every 8 seconds, and the spatially filtered wavefront sensor. It also uses a Linear-Quadratic-Gaussian (LQG) controller (aka Kalman filter) for both pointing and focus. We present on-sky performance results from...

Topics: Instrumentation and Methods for Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.2278

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Jul 8, 2014
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Jul 8, 2014
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Zachary H. Draper; Christian Marois; Schuyler Wolff; Marshall Perrin; Patrick Ingraham; Jean-Baptiste Ruffio; Fredrik T. Rantakyrö; Markus Hartung; Stephen J. Goodsell; with the GPI team

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The Gemini Planet Imager (GPI) is an instrument designed to directly image planets and circumstellar disks from 0.9 to 2.5 microns (the $YJHK$ infrared bands) using high contrast adaptive optics with a lenslet-based integral field spectrograph. We develop an extraction algorithm based on a least-squares method to disentangle the spectra and systematic noise contributions simultaneously. We utilize two approaches to adjust for the effect of flexure of the GPI optics which move the position of...

Topics: Instrumentation and Methods for Astrophysics, Earth and Planetary Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1407.2309